<?php

 if(!isset($_COOKIE['username'])){
	    setcookie ("nav",'',time()-3600);
		setcookie ("username",'',time()-3600);
        header ( 'Location: index.php' );
	}

?>

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>后台</title>
<style>
.nav{width:100%;height:20px}ul,li{margin:0;padding:0}li{float:left;list-style-type:none;margin-right:10px;display:block}		
</style>
</head>
<body>
<?php
echo "你好，欢迎你". $_COOKIE['username'];
?>
<hr>
<ul class="nav">
  <li><a href="index.php">返回首页</a></li>
  <li><a href="conn.php?login=out">安全退出</a></li>
</ul>
</body>
</html>